Hello,
I recently started with the Adafruit HUZZAH ESP8266 Breakout board to add Wi-Fi to my project and use AT commands. After many hours of reading and trial-and-error, i managed to flash a recent AT firmware and then got some promising results from PuTTY. All seemed fine, until i connected it to my Arduino UNO and then powered it via the 5V on-board pin. I connected a 7.4 V battery to my Arduino and then the ESP8266 metal housing get really hot (too hot to touch) very quickly, usually within a few seconds. I connected it to PuTTY again and it's returning some gibberish text and AT commands are no longer working. I tried to ground the GPIO0 pin via a 220 Ohms resistor but that didn't help. Now, all i see when i power it, is the dim red light near the text GPIO0. I think it might be stuck in bootload mode but the heating is what's worrying me a lot since i cannot keep it connected to the FTDI cable for more than a few seconds. I tried flashing AT firmware back on it, but the module gets so hot that it fails partly through the firmware flashing process.
Is the HUZZAH ESP8266 irreparably damaged? I thought it was more robust given all the pull-up/down resistors and the level shifter on the PCB. I never got to use it and paid quite a lot with import taxes from USA to EU in my country. 